Q. When and by whom the term Neoplatonism was created?

A. Who? It was probably Thomas Taylor, who translated early works into English.
When? A quick web search produces results like "modern," "late 18th and early 19th centuries" and "early 19th century". If it was in fact Taylor who coined the term, one can say for certain it was some time before 1 November 1835, the day he died!
I can not find the first issue date for his book, "Proclus the Neoplatonic Philosopher", although the first edition of "Proclus: Proclus' Commentary on the Timaeus of Plato" is dated 1816.
I'll guess he created the term Neoplatonism in the 18-teens to the 18-twenties (or thereabouts).
A search through the ISNS site: http://www.isns.us/texts.htm could lead to a more precise date, but for now, that's all I've got.